1. Field of the Invention
The present invention relates to an image processing apparatus and an image processing method, and particularly, to an image processing apparatus and an image processing method capable of image processing with a small memory area.
2. Description of the Related Art
In the related art, there exist image processing apparatuses which appropriately process image data transmitted from upper level devices such as a computer or a scanner, and output the image data to an image output device. For example, Japanese Laid-Open Patent Application No. 11-227263 (below, referred to as “reference 1”) discloses a technique in this field.
Below, descriptions are made of an image processing apparatus in the related art.
FIG. 1 is a block diagram exemplifying a configuration of an image processing apparatus in the related art.
As an example, in FIG. 1, a printer system is used as the image processing apparatus in the related art. In addition, in the following descriptions, bitmap image data are used as an example of the image data subject to image processing.
As shown in FIG. 1, an image processing apparatus 100 includes a computer 101 functioning as an upper-level device, a printer controller 102 serving as a control unit, and a printer engine 103 serving as an image output unit.
The computer 101 includes an image data input unit 111, a data compression unit 112, and a transmission memory 113.
The image data input unit 111 receives the bitmap image data from image data stored in a memory (not illustrated) of the computer 101, or image data stored in other devices connected through wireless or cable communication networks such as telephone lines or LAN (Local Area Network) cables. In addition, the image data input unit 111 outputs the received bitmap image data to the data compression unit 112.
The data compression unit 112 compresses the received image data to form image data of a format supported by a printer driver, and outputs the compressed image data to the transmission memory 113.
The transmission memory 113 stores the compressed image data and outputs a preset amount of the compressed image data to the printer controller 102 at preset timings.
The printer controller 102 includes a reception memory 121, a data decompression unit 122, a frame memory 123, an image processing unit 124, and a line memory 125. The printer controller 102 receives the compressed image data from the computer 101, and stores the compressed image data in the reception memory 121.
The data decompression unit 122 decompresses the image data received from the reception memory 121 and generates the bitmap image data, and outputs the decompressed bitmap image data to the frame memory 123.
The frame memory 123 stores an amount of the bitmap image data equivalent to one frame (one picture), and outputs the stored bitmap image data to the image processing unit 124.
The image processing unit 124 performs color correction, color transformation, dither processing, edge processing, and other image processing on the bitmap image data, and outputs the processed image data to the line memory 125.
The line memory 125 outputs the image data to the printer engine 103, for example, by means of FIFO (First-In First-Out).
The printer engine 103 generates and outputs printing images from the image data received from the printer controller 102.
It should be noted that processes in the printer system 100 as shown in FIG. 1 are for generating monochromatic images. When generating color images, for example, with a color printer, it is necessary to generate CMYK images, that is, Cyan (C), Magenta (M), Yellow (Y), Black (K) images. For this purpose, usually, it is required to repeat the above-described processes four times. In this case, the speed of generating a color image is reduced to one-fourth of that for forming a monochromatic color.
In order to realize a high-speed color printer having high speed for printing color images, a tandem-type printer engine was proposed. The tandem-type printer engine has four image generation units and can generate CMYK four color images at the same time. With the tandem-type printer engine, the speed of generating a color image is the same as that of generating a monochromatic color.
Below, a printer controller adapted to support the tandem-type printer engine is described.
FIG. 2 is a block diagram exemplifying a configuration of a printer controller for a tandem-type operation.
As shown in FIG. 2, a printer controller 202 includes a reception memory 221, a data decompression unit 222, a frame memory 223, image processing units 224-1 to 224-4, and line memories 225-1 to 225-4.
The printer controller 202 receives the compressed image data from the computer 101, and stores the compressed image data in the reception memory 221.
The data decompression unit 222 decompresses the image data received from the reception memory 221 and generates the bitmap image data, and outputs the decompressed bitmap image data to the frame memory 223.
The image processing units 224-1 to 224-4 carry out color correction, color transformation, dither processing, edge processing, and other image processing on the bitmap image data for the four colors, respectively, output the processed image data to the printer engine 103 through the corresponding line memories 225-1 to 225-4. Usually, the line memories 225-1 to 225-4 for different colors have different capacities.
FIG. 3 is a block diagram illustrating a configuration of a tandem-type printer engine.
As shown in FIG. 3, a tandem-type printer engine 301 includes exposure units 311-1 through 311-4, photosensitive drums 312-1 through 312-4, developing units 313-1 through 313-4, and an intermediate transfer 314. In the tandem-type printer engine 301, the exposure units 311-1 through 311-4 expose corresponding printing colors, for example, CMYK, on the photosensitive drums 312-1 through 312-4 to form electrostatic latent images thereon; the developing units 313-1 through 313-4 develop the respective latent images to form monochromatic images of the CMYK printing colors on the photosensitive drums 312-1 through 312-4, respectively; these monochromatic images are superposed on the intermediate transfer 314 and are transferred to a recoding medium 315 to form a color image thereon.
However, as shown in FIG. 3, in a tandem-type printer, the timings of operating the exposure units 311-1 through 311-4 change depending on intervals between the CMYK photosensitive drums 312-1 through 312-4. Due to this, the color handled at a later timing produces a larger amount of data, and requires a line memory of a larger capacity. Therefore, in order to maintain the high printing speed when using the tandem type printer, the hardware resources and the memory capacity need be increased fourfold, and thus, the cost of the whole image processing apparatus increases.